Method of monitoring the effectiveness of a damper, and a device for implementing said method

Abstract

The present invention relates to a method of monitoring the effectiveness of a damper system, wherein the method consists in measuring the relative movements of two strength members, in filtering the measurements in order to isolate those that relate to the lead-lag resonant frequency of the blade, in rectifying the signal, in recording the signal, in comparing the rectified signal (S) with a threshold value (S L ), in determining an initial time interval (T 0 ) as soon as the rectified signal exceeds the threshold value (S L ), in calculating the integrals of the signal from T 0 to T 0 +δ and from T 0 to T 0 +pδ, in calculating the ratio R of the integrals, and in comparing the ratio R with a limit value R L , and in activating and delivering an alert signal (V 1 ) if the ratio R is greater than or equal to the limit value R L .

What is claimed is: 
     
       1. A method of monitoring the effectiveness of a damper system for damping the movement components of equipment of an aircraft that result from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and that are connected together by a damper member, the method comprising:
 a) measuring, with a movement sensor, the relative movements of the two strength members; 
 b) filtering, with an electronic filter, the measurements to isolate those that relate to the lead-lag resonant frequency of the equipment; 
 c) rectifying, with an electronic circuit, the signal that results from the filtering; 
 d) recording the rectified signal (S); 
 e) comparing, with a comparator circuit, the rectified signal (S) with a predetermined threshold value (S L ) and returning to step a) so long as the rectified signal (S) does not exceed said threshold value (S L ); 
 f) determining an initial time instant T 0  as soon as the rectified signal exceeds the threshold value (S L ); 
 g) calculating, with an integrator circuit, an integral I 1  of the rectified signal from T 0  to T 0 +δ, where δ is a predetermined time interval characteristic of the damped equipment; 
 h) calculating, with the integrator circuit, an integral I p  of the rectified signal from T 0  to T 0 +pδ, where p is an integer equal to 2, 3, 4, or 5; 
 i) calculating a ratio R where R=I p /I 1 ; 
 j) comparing the ratio R with a predetermined limit value R L ; 
 k) returning to step a) if the ratio R is less than the limit value R L ; 
 l) activating and delivering an alert instruction (V 1 ) if the ratio R is greater than or equal to the limit value R L , said alert instruction corresponding to a failure of the damper system; and 
 m) using an electrical power supply to operate at least the filter and the circuits. 
 
     
     
       2. An effectiveness monitoring method according to  claim 1 , further comprising using an integer p=3. 
     
     
       3. An effectiveness monitoring method according to  claim 1 , that is implemented continuously on equipment while in operation. 
     
     
       4. An effectiveness monitoring method according to  claim 1 , further comprising using pre-established and recorded values for the lead-lag resonant frequency (ω δ ), for the threshold value (S L ), for the limit value R L , and for the characteristic time δ. 
     
     
       5. An effectiveness monitoring method according to  claim 1 , wherein the aircraft equipment is a rotor blade. 
     
     
       6. An effectiveness monitoring method according to  claim 1 , further comprising monitoring the operating state of the means implementing said monitoring method and delivering at least one additional alert signal (V 2 ) in the event of malfunction. 
     
     
       7. An effectiveness monitoring method according to  claim 1 , wherein the limit value R L  is initially determined theoretically and is subsequently corrected as a function of experimental results from flight testing. 
     
     
       8. A method of monitoring the effectiveness of a damper system for damping the movement components of equipment of an aircraft that result from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and that are connected together by a damper member, the method comprising:
 a) measuring, with a movement sensor, the relative movements of the two strength members; 
 b) filtering, with an electronic filter, the measurements to isolate those that relate to the lead-lag resonant frequency of the equipment; 
 c) rectifying, with an electronic circuit, the signal that results from the filtering; 
 d) recording the rectified signal (S); 
 e) comparing, with a comparator circuit, the rectified signal (S) with a predetermined threshold value (S L ) and returning to step a) so long as the rectified signal (S) does not exceed said threshold value (S L ); 
 f) determining an initial time instant T 0  as soon as the rectified signal exceeds the threshold value (S L ); 
 g) calculating, with an integrator circuit, an integral I 1  of the rectified signal from T 0  to T 0 +δ, where δ is a predetermined time interval characteristic of the damped equipment; 
 h) calculating, with the integrator circuit, an integral Ip of the rectified signal from T 0 +pδ to T 0 +(p+1)δ, where p is an integer equal to 2, 3, 4, or 5; 
 i) calculating a ratio R where R=I p /I 1 ; 
 j) comparing the ratio R with a predetermined limit value R L ; 
 k) returning to step a) if the ratio R is less than the limit value R L ; 
 l) activating and delivering an alert instruction (V 1 ) if the ratio R is greater than or equal to the limit value R L , said alert instruction corresponding to a failure of the damper system; and 
 m) using an electrical power supply to operate at least the filter and the circuits. 
 
     
     
       9. An effectiveness monitoring method according to  claim 8 , further comprising using an integer p=3. 
     
     
       10. An effectiveness monitoring method according to  claim 8 , that is implemented continuously on equipment while in operation. 
     
     
       11. An effectiveness monitoring method according to  claim 8 , further comprising using pre-established and recorded values for the lead-lag resonant frequency (ω δ ), for the threshold value (S L ), for the limit value R L , and for the characteristic time δ. 
     
     
       12. An effectiveness monitoring method according to  claim 8 , wherein the aircraft equipment is a rotor blade. 
     
     
       13. An effectiveness monitoring method according to  claim 8 , further comprising monitoring the operating state of the means implementing said monitoring method and delivering at least one additional alert signal (V 2 ) in the event of malfunction. 
     
     
       14. An effectiveness monitoring method according to  claim 8 , wherein the limit value R L  is initially determined theoretically and is subsequently corrected as a function of experimental results from flight testing. 
     
     
       15. A device to monitor the effectiveness of a damper system for damping the movement components of equipment of an aircraft resulting from the lead-lag resonant frequency (ω δ ) of said equipment, said damper system including two strength members that are movable relative to each other and connected together by a damper member, the device comprising:
 a self-contained power supply unit; 
 a movement sensor for measuring the relative movements of the strength members; 
 a bandpass filter for isolating the movement components of the strength members that result from the lead-lag resonant frequency (ω δ ); 
 a diode bridge for rectifying the signal delivered by the bandpass filter; 
 recording means including a memory for storing the rectified signal; 
 a comparator circuit for determining the time T 0  at which the value of the rectified and filtered signal exceeds a predetermined threshold value (S L ), making use of an additional memory and a clock; 
 an integrator circuit for calculating the integral I 1  of the signal from time T 0  to T 0 +δ and the integral I p  from T 0  to T 0 +pδ or from T 0 +pδ to T 0 +(p+1)δ, where p is an integer equal to 2, 3, 4, or 5, and where δ is a predetermined time interval characteristic of the damped equipment; 
 another comparator circuit for calculating the ratio R where R=I p /I 1 , and for comparing said ratio R with a predetermined limit value R L ; and 
 means for activating or deactivating a visual indicator as a function of the signal coming from the other comparator circuit. 
 
     
     
       16. A device according to  claim 15 , including means for monitoring the operating state of said device and means for activating or deactivating at least one additional visual indicator.